Signaling device for telephone-exchanges.



No. 897,731. PATENTED SEPT. 1, 1908.

' T. W. GARDNER.

SIGNALING DEVICE FOR TELEPHONE EXCHANGES.

APPLICATION nun FEB.16, 1 905.

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per q A arm .s

THOMAS WEST GARDNER, OF NASHVILLE, TENNESSEE.

SIGNALING DEVICE FOR TELEPHONE-EXCHANGES.

Specification of Letters Patent.

Patented Sept. 1, 1908.

Application filed February 15, 1905. Serial No. 245,728.

Signaling Devices for Telephone-Exchanges,

of which the following is a specification.

My invention relates to nnprovements in signaling devices for the equipment of telephone exchanges of the common battery type, the objects of the invention being first, to make provision for obtaining the busy test click in systems in which the cord circuit transmission is of the condenser type.

It is further desired to provide a novel combination of apparatus for controlling the operation of the supervisory signal.

I attain these objects by the arrangement of apparatus and connecting wires, illustrated in the accompanying drawing, in which z The figure is a diagrammatic view illustrating my invention as applied to a telephone system in which the cord circuit is of the condenser transmission type.

In the above drawings, 9 and Q2, and q and Q3, are the receivers and transmitters, respec tively, of two subscribers, while and j are jacks connected in the well known manner. One of the talking wires, as 1, is connected to a source of electrical energy I) (in the present instance a battery) through a winding of a relay 0 which has a second winding interposed between the second talking wire 2 and the ground. These two windings being on a common core form a balanced impedance coil and actuate an armature, serving as a double pole switch whose pivoted terminal is grounded. Another terminal 1" of this switch is connected through a second switch a with the line signal lamp m while the third terminal 8 is connected to a line 3. This line connects at one end with the test rings h of all the acks j, while its other end is grounded through a winding a of relatively high resistance which also serves to actuate the switch a. In the operators circuit are the customary supervisory signal lamps L and L, together with a condenser 25 in series with the operators telephone and balanced impedance coils p, two of which terminals are respectively connected to the terminals of the operators talking circuit while the other two terminals of said coils are respectively connected to the terminals of the generator I). There is also the well known combination ringing and listening key is and the second cord plug The apparatus employed in connection with the second subscribers instruments g and (f, being a duplication of that previously noted in connection with the instruments Q and Q, will not be described in detail.

When the receiver is removed from its hook, a circuit is completed from battery I) through the windings of relay 6, drawing up armature of said relay. The motion of this relay causes the opening of contact 8 and the closing of local contact 1. The closing of contact 1" completes a local circuit from battery I) through line signal m by way of back contact n of relay (1, which illuminates said line signal. The operator in response inserts plug g in jack j, which operation, in addition to making metallic connection with talking wires 1 and 2, closes a circuit from battery I) by way of wires 4, through su ervisory signal L and sleeve of plug 9, said sleeve making metallic contact wlth test ring it of jack j, incidentally providing change of polarity, thence through wires 3 and winding of relay a. Now, winding of relay a is sufliciently high in ohmic 1'6S1Sl3 nce to prevent illumination of supervlsory signal L, when said supervlsory signal and wmdmg are thrown 1n series relation, but relay (1 is sufficiently sensitive to operate quickly and positively in the same series circuit with supervisory signal L. The operation of said relay opens contact it, thus disconnecting and extinguishing line signal m. After learning the desired number, the operator inserts the calling plug f into the jack j of the line wanted and 0 erates ringing key 76, ringing subscribers liell in the usual manner, said line being indicated by 6 and 7. The placing of plug f in jack y" closes a circuit from battery I) by way of wire 5 through supervisory signal L, sleeve of plug f, test ring 7L, and back contact 8 of relay 6, thus causing the illumination of said supervisory signal L. Upon the removal of receiver 9 and the subse quent operation of relay 6, the shunt path around relay a is broken by opening of contact 8, thus placing winding of relay a in series relation with supervisory signal L. As before stated, the ohmic resistance of said winding is sufiiciently high to prevent the illumination of supervisory signal, and in this manner said signal is extinguished. Thesevarious operations having been gone through with, the two subscribers receive nals L and L. The operator upon the illumination of said signals withdraws the plugs f and 9.

Provision for obtaining the busy test click in connection with the condenser transmission method is made by the insertion in the operators telephone circuit of the bridged impedance coil 10. This coil is of high ohmic resistance and impedance, consisting of two balanced windings on the same core and designed to operate in connection with the battery I) to keep the condenser t (which is in series with operators telephone a) charged continually. Upon throwing listening key 76 the tip of the plug f is brought into metallic connection, through one winding of the coil 10, with the same pole of battery 6 as is connected with the test rings h of all the jacks j, 7', etc, of the idle lines. Thus, upon testing the ring it of the jack of an idle line no current is caused to flow, but, as before stated, the polarity of said test rings is reversed while line is in use. After this reversal, upon making the test with the tip of the plug, a circuit is completed through a winding of coil p which, since this latter is of high impedance,

does not result in any sudden flow of current. The momentary drop of potential, however, causes the discharge of condenser 25 through the operators head telephone, giving the busy click.

I claim as my invention 1. A tele hone system including a source of electrica energy, a central exchange, an operators set, two balanced windings having a common core, a condenser in series with the operators head receiver, and connections between said apparatus such that the condenser is maintained in a charged condition by the battery and said windings, substantially as set forth.

2. A telephone system including a source of electrical energy, a central exchange, an operators set, two balanced windings having a common core, a condenser in series with the operators head receiver, and connections between said apparatus such that the condenser is maintained in a charged condition by the battery and said windings, and means for connecting a terminal of the operators plug to one of said windings, the connections of the system being such that a terminal of a jack in use has a polarity difiierent from that of said plug terminal, substantially as set forth.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses.

THOMAS WEST GARDNER.

Witnesses:

J. W. HUNTER, Jr., H. G. GR EN. 

